1. Field of the Invention
The present invention relates to methods and apparatus for concentrating and collecting solar energy for many uses including the conversion thereof to heat energy and/or electrical energy to be used for many purposes. The present invention also relates to the storage and use of heat energy during hours without sunshine or with reduced sunshine. The present invention further relates to the treatment of liquids including water containing salt and/or other substances using fixed and portable apparatus and methods according to the invention. More particularly, the invention relates to methods and apparatus using fluid and/or Fresnel concentrating lenses and lens systems and elongated collectors comprising at least one fluid-carrying conduit located at the foci of the lenses.
2. Description of the Prior Art
The energy emitted by the sun corresponds to a high temperature in the order of 6000.degree. C., and is emitted in the form of radiation which arrives at the earth with a wavelength distribution comprising about 3% ultraviolet rays, 42% visible light rays, and about 55% infrared rays. It is well known that surfaces exposed to the sun collect at least to some degree the solar radiation and that the absorption of this radiation results in a heating of the material constituting the surface. It is also known that electricity can be produced by photoelectric devices exposed to the sun's rays.
There have been many attempts in the past to collect and utilize pollution-free and essentially nonconsumable solar energy to meet many energy needs. Much attention has been directed to the conversion and utilization of solar energy in the past few years because of the realization that fossil fuels are exhaustible and that a burning of these fuels produces pollution. Solar energy is inexhaustible and available above the clouds at an average energy level of approximately 1350 watts per horizontal square meter. A percentage of this energy, depending on atmospheric and weather conditions, dust, pollution, etc., is available at the surface of the earth during periods of sunshine which vary up to about 4000 hours per year depending on location. Even more recently, the shortage of fossil fuels particularly oil and natural gas and the high cost thereof have sparked new attempts to harness the energy of the sun. Heretofore, however, fuels were a less expensive source of energy than solar energy and the same problem of high capital cost and the cyclic nature of the sun requiring storage capability have heretofore not been satisfactorily solved. For example, refringent lens focusing systems, most using reflecting collectors, have heretofore been used but are uneconomical and impractical because of the high cost involved. A conventional system for obtaining lower temperatures up to about 80.degree. C. consists of dark-colored panels absorbing the solar radiation and means for removing the heat from the panels such as a fluid system circulating a heat-carrying fluid in a heat-exchanging manner with the panels. It is also known to improve the efficiency of these systems by placing one or more glass plates above the panels to produce a greenhose effect for reducing heat losses. However, the efficiency of these panel systems is low, from about 30% to about 40%, and they require large spaces resulting in large heat losses, and they also require a high capital investment. The use of Fresnel-type lenses and fluid lenses is known in the art for focusing solar energy. See, for example, U.S. Pat. Nos. 3,915,148; 3,125,091; 937,013; 3,965,683; 3,901,036; 60,109; 1,081,098; Japanese Pat. No. 28-2130, and Australian Pat. No. 131,069. However, none of the known systems is capable of converting and storing solar energy efficiently and none can produce heat at an economical capital investment such that the use of solar energy is competitive with other forms of energy. The prior art also does not disclose obtaining temperatures in the order of a few hundred degrees C. while also obtaining at the same time lower temperatures usable for home heating and water heating or other purposes. Nor is there in the prior art a system which is capable of storing heat energy from solar energy during periods of interrupted sunshine for any length of time and which also is capable of providing different temperatures simultaneously and also utilizing the luminous and utilizing or dispersing the heat produced by the infrared rays of the sun.
With respect to electrical generation, it is known that concentrating the solar energy at a photovoltaic cell will increase the electrical output of cell; however, there is the disadvantage that the increased heat in the photovoltaic cell resulting from the concentration will also limit the cell output. Known photovoltaic devices produce a maximum of about one watt per hour per cell. Assuming a cost of $10 per photovoltaic cell, a system using non-concentrated solar energy to generate about 1 kilowatt per hour requires a capital cost of at least $10,000 which is not competitive for normal uses.
With respect to solar stills, known stills used for distillation of seawater have low efficiencies and the cost of heating the water is high as the least amount of heat required to vaporize the water is not recovered from condensation but rather is lost.
In accordance with the invention the prior art drawbacks and disadvantages are substantially overcome and additional advantages realized.